ATP release via connexin hemichannels controls intercellular propagation of Ca2+ waves in corneal endothelial cells

Abstract

Intercellular communication (IC) is essential for coordinating cellular activity in multi-cellular organisms, and plays a role in many physiological and pathological processes. Direct IC between adjacent cells is mainly mediated by gap junctions, whereas paracrine signaling provides an indirect pathway for IC between neighboring cells. Purinergic mediators are important messengers in this paracrine signaling, and recent evidence shows that connexin and pannexin hemichannels form an important release pathway for ATP involved in purinergic IC. We have investigated the properties of IC via Ca2+ waves evoked by mechanical stimulation of a single cell in monolayers of bovine corneal endothelial cells (BCEC). We have demonstrated that both gap junctions and paracrine IC are involved in the Ca2+ wave propagation, and that purinergic paracrine signaling is the main component of IC in BCEC. Furthermore, our results demonstrate that connexin43 hemichannels provide the pathway for ATP release. Our experiments show that the paracrine IC is strongly reduced in the presence of inflammatory agents, such as histamine and thrombin, that enhance actomyosin contraction. The effect of these agents is due to inhibition of hemichannel-mediated ATP release. This effect of thrombin can be precluded by preincubation of the cells with adenosine. Possible roles of paracrine IC to bystander and good Samaritan effects are discussed. © Springer Science+Business Media B.V. 2010.